1. Field of the Invention
The present invention relates to airbag inflation apparatuses for use in motor vehicles and, more specifically, to a cover of a bolster panel for a knee airbag system.
2. Technical Background
Inflatable airbags are well accepted in their use in motor vehicles and have been attributed with preventing numerous deaths in accidents. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits and vehicle owners are frequently willing to pay the added expense for airbags.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartment. If the vehicle has a driver bag only, the ECU may be mounted in the steering wheel. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of the inflator or gas generator which, in some embodiments, uses a combination of compressed gas and solid fuel. The inflator inflates a textile airbag to impact a passenger and prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover covers a compartment containing the airbag module and may reside on a steering wheel, dashboard, vehicle door, or vehicle wall. The airbag cover is typically made of a rigid plastic and may be forced opened by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover freely moves into the passenger compartment, it may injure a passenger.
Airbag apparatuses have been primarily designed for deployment in front of the torso of an occupant. More specifically, airbags are disposed for deployment between the upper torso of an occupant and the windshield and instrument panel. During a front end collision, there is a tendency for an occupant, particularly one who is not properly restrained by a seat belt, to slide forward along the seat and xe2x80x9csubmarinexe2x80x9d under the airbag (hereinafter referenced as the xe2x80x9cprimary airbagxe2x80x9d).
In order to prevent such an occurrence, a knee airbag system has been developed to engage an occupant""s knees or lower legs and prevent submarining under the primary airbag. The knee airbag system includes a knee airbag which deploys during an accident to restrain forward movement of an occupant""s knees and legs. The knee airbag system may also include a fixed panel, referred to as a knee bolster panel, which is disposed in front of a knee airbag. The knee bolster panel provides a more rigid surface area than an airbag alone to better engage the knees or lower legs of an occupant to thereby restrain the occupant""s lower body. The knee bolster panel may provide some degree of deformation to minimize the impact to an occupant.
Knee airbag systems are located in the lower portion of an instrument panel. The system further includes a cover which is attached to the bolster panel and generally conforms to the contour of an exterior surface of the instrument panel. The cover may attach to the bolster panel through use of fasteners such as rivets, clips, or other snap-fit devices. The fasteners may be molded into the cover or may be separate components. In conventional systems the fasteners extend from the cover and through the bolster panel to the extent that they may contact the airbag. As the fasteners are sharped edged devices, they may puncture or otherwise tear the airbag. The airbag is particularly susceptible to punctures from the fasteners when the fasteners are initially driven through the bolster panel. Obviously, a torn airbag will not inflate properly and provide the full intended cushion effect.
It would therefore be an advancement in the art to provide a knee airbag system which prevents contact between the fasteners and the airbag to avoid tearing. It would be a further advancement in the art to provide a simple and economical solution to prevent contact between the fasteners and the airbag. Such a device disclosed and claimed herein.
The present invention is a knee airbag system with a bolster panel that is disposed between an inflatable airbag and a cover. The bolster panel is secured to the cover through the use of one or more fasteners. The bolster panel is configured with one or more trenches or wells that provide recess spaces. The fasteners extend from the cover and pass through the bolster panel and into a recess space provided by the trench or well. The recess space has a depth that is greater than the protruding portion of the fastener to prevent the fastener from contacting the airbag. The airbag may be secured to bolster panel by passing a portion of the airbag through a retention aperture in the bolster panel. The portion of the airbag then passes around a retention rod that has a diameter greater than the retention aperture. In order to prevent a portion of the airbag from entering a recess space, the airbag is secured to the bolster panel so as to limit slack. The present invention provides a cost effective and practical solution to reduce risks of airbag tears while still retaining the use of fasteners.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.